5.1 Microbial Nutrition

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Lecture 5

• 5.1 Microbial Nutrition
• 5.2 Culture Media
• 5.3 Laboratory Culture of Microorganisms
• 6.1 Cell Growth and Binary Fission
• 6.2 Peptidoglycan Synthesis and Cell Division
• 6.3 Population Growth
• 6.4 The Growth Cycle
• 6.5 Direct Measurements of Microbial Growth
• 6.6 Indirect Measurements of Microbial Growth

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Overview of Cell Metabolism
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Energy Classes of Microorganisms

• phototrophs light as energy source
• chemotrophs chemicals as energy source
• chemoorganotrophs organic chemicals
• chemolithotrophs inorganic chemicals

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Culture Media

• Defined - made from purified chemicals
• Complex - exact chemical composition not known

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Liquid
Solid
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Binary Fission
Some bacteria can complete one generation in as
little as 20 min.
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Bactoprenol
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Population Growth

• Growth rate change in cell / time
• Generation time (g) time for formation of two
  cells from one doubling time
• If generation time remains constant, then
  exponential growth

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Rate of Growth in Culture
Doubling Time 30 min Exponential Growth
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Calculation of Generation Time
Slope log 2 / g 0.301/g
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Stationary Phase

• A single cell with generation time of 20 min ? a
  population after 48 h that would weigh 4000 times
  the weight of the earth.
• Growth is limited by the lack of an essential
  nutrient or the production of inhibitory waste
  product

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Direct Microscopic Count
Petroff-Hauser counting chamber
Requires at least 106 cells/ml
Counts all cells cannot distinguish between
living and dead
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Viable Count
CFU colony forming unit
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Serial Dilutions
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Turbidity Measurements
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